An LTPS TFT liquid crystal display (LCD) is different from a conventional amorphous (a-Si) TFT-LCD. The conventional amorphous material only has an electron mobility of 0.5 cm2/V·sec, while LTPS has an electron mobility up to 50-200 cm2/V·sec. Therefore, as compared with the conventional a-Si TFT-LCD, the LTPS TFT-LCD has advantages like improvements in term of resolution, response time, aperture ratio, and brightness. Furthermore, an increased electron mobility enables the peripheral driving circuit to be integrated onto a glass substrate, which realizes an integrated system on glass (SOG) and saves space and cost.
In the existing LTPS process, an interface between a polysilicon (P-Si) active layer and a gate insulating layer (GI) is generally subject to a gate insulating layer pre-cleaning (Pre-GI Clean) process. Namely, prior to forming the gate insulating layer, the surface of P-Si active layer is subject to pre-cleaning. This pre-cleaning process can only improve the roughness of the interface between the active layer and the gate insulating layer and reduce interfacial state defect density to an extent. Further, products of different specification may need different pre-cleaning processes, which increases the process complexity and time cost.
Therefore, there is a need for an improved LTPS TFT and a method for fabricating the same.